Reduce some n+1 queries on admin document show and edit views
Do some n+1 reduction on the new forms for documents

The most impactful was the changes to the role_appointments which brings the speeches page down to 7s (from 18s on my machine).  It's still slow, but it's in the same ballpark as the other forms now.
Fix localised_path_helper to fallback to I18n.locale if not provided

This stops it asking if the object is available in locale: 'NULL' and slowing pages down unnecessarily in the normal case.
Remove transitioning orgs from the home page

There aren't any more transitioning ministerial depts (woo) and we're not going to share the tranisitoning ALBs (there's a redesign coming anyway) so doing the query is busy work.
Remove unscoped index for document series in admin

The full list was slow and adding pagination would mean adding search or filtering, so instead we redirects you to the document series list for your org (or the org list if you don't have one).

The delete button now appears on the show page for the doc series too.
Turn Edition#last_author into an association so it can be eager-loaded
de-n+1-ify the fact check requests in admin
Merge pull request #573 from alphagov/n-plus-one-for-admin

N+1 improvements for admin